Topic 4: Ecology
4.1 Species, communities and ecosystems
Essential idea: The continued survival of living organisms including humans depends on sustainable communities.
Nature of Science: Looking for patterns, trends and discrepancies—plants and algae are mostly autotrophic but some are not
Understandings:
● Species are groups of organisms that can
potentially interbreed to produce fertile
offspring.
●
Members of a species may be reproductively
isolated in separate populations.
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Species have either an autotrophic or
heterotrophic method of nutrition (a few species
have both methods).
●
Consumers are heterotrophs that feed on living
organisms by ingestion.
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Detritivores are heterotrophs that obtain organic
nutrients from detritus by internal digestion.
●
Saprotrophs are heterotrophs that obtain organic
nutrients from dead organisms by external
digestion.
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A community is formed by populations of
different species living together and interacting
with each other.
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A community forms an ecosystem by its
interactions with the abiotic environment.
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Autotrophs obtain inorganic nutrients from the
abiotic environment.
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The supply of inorganic nutrients is maintained
by nutrient cycling.
●
Ecosystems have the potential to be sustainable
over long periods of time.
4.2 Energy flow
Essential idea: Ecosystems require a continuous supply of energy to fuel life processes and to replace energy lost as heat.
Nature of Science: Use theories to explain natural phenomena—the concept of energy flow explains the limited length of food chains
Understandings:
● Most ecosystems rely on a supply of energy
from sunlight.
● Light energy is converted to chemical energy in
carbon compounds by photosynthesis.
●
Chemical energy in carbon compounds flows
through food chains by means of feeding.
●
Energy released from carbon compounds by
respiration is used in living organisms and
converted to heat.
●
Living organisms cannot convert heat to other
forms of energy.
●
Heat is lost from ecosystems.
●
Energy losses between trophic levels restrict the
length of food chains and the biomass of higher
trophic levels.
4.3 Carbon Cycling
Essential idea: Continued availability of carbon in ecosystems depends on carbon cycling.
Nature of Science: Making accurate, quantitative measurements—it is important to obtain reliable data on the concentration of carbon dioxide and methane in the
atmosphere
Understandings:
● Autotrophs convert carbon dioxide into carbohydrates and other carbon
compounds.
●
In aquatic ecosystems carbon is present as dissolved carbon dioxide and
hydrogen carbonate ions.
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Carbon dioxide diffuses from the atmosphere or water into autotrophs.
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Carbon dioxide is produced by respiration and diffuses out of organisms
into water or the atmosphere.
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Methane is produced from organic matter in anaerobic conditions by
methanogenic archaeans and some diffuses into the atmosphere or
accumulates in the ground.
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Methane is oxidized to carbon dioxide and water in the atmosphere.
●
Peat forms when organic matter is not fully decomposed because of
acidic and/or anaerobic conditions in waterlogged soils.
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Partially decomposed organic matter from past geological eras was
converted either into coal or into oil and gas that accumulate in porous
rocks.
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Carbon dioxide is produced by the combustion of biomass and fossilized
organic matter.
●
Animals such as reef-building corals and mollusca have hard parts that
are composed of calcium carbonate and can become fossilized in
limestone.
4.4 Climate Change
Essential idea: Concentrations of gases in the atmosphere affect climates experienced at the Earth’s surface.
Nature of Science: Assessing claims—assessment of the claims that human activities are producing climate change.
Understandings:
● Carbon dioxide and water vapour are the most significant greenhouse
gases.
●
Other gases including methane and nitrogen oxides have less impact.
●
The impact of a gas depends on its ability to absorb long wave radiation
as well as on its concentration in the atmosphere.
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The warmed Earth emits longer wavelength radiation (heat).
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Longer wave radiation is absorbed by greenhouse gases that retain the
heat in the atmosphere.
●
Global temperatures and climate patterns are influenced by
concentrations of greenhouse gases.
●
There is a correlation between rising atmospheric concentrations of
carbon dioxide since the start of the industrial revolution 200 years ago
and average global temperatures.
●
Recent increases in atmospheric carbon dioxide are largely due to
increases in the combustion of fossilized organic matter.